This meeting is the third in a series of international conferences held every five years, which focuses on the structure and function of the ubiquitous cellular protein actin. It is of considerable significance that the proposed conference will be the first meeting devoted to the fundamental properties and cellular function of actin and the actin-based microfilament system since the molecular structure and cation/ATP binding sites have been elucidated by x-ray crystallography. This three-day conference will focus on a specific agenda concentrating on such topics as (1) basic properties of the actin molecule and actin-based microfilament systems; (2) actin-associated proteins and control of filament assembly/disassembly; and (3) the cellular functions of the microfilament system. Participants will include scientists from a number of disciplines who are actively involved in basic research in cell motility, microfilament structure, and gene regulation (the latter area is expected to heavily focus on the use of genetic techniques to manipulate expression of specific actin-associated proteins in cultured cells). Oral presentations on each day will emphasize a specific topic area and be offered by key researchers in each area as invited by the organizing committee. These presentations will be followed by an open discussion led by the chairperson of each session. Poster sessions will be scheduled for late afternoon-early evening to maximize group discussion by all participants (in particular younger scientists and graduate students who will be encouraged to attend and actively participate in these conference proceedings). The detailed conference plan lists the names of approximately 24 scientists who will be invited to participate with the understanding that most of them will constitute the group of formal presenters, invited discussants, and session chairpersons. The recent realization of the role of actin in trans-membrane signalling events, the resolution of the crystal structure of the actin molecule, and the rapid advances in the ability to manipulate the microfilament system via genetic techniques necessitates this conference as a vehicle to transmit timely information among the most active participants in a field of enormously rapid growth.